The sensory organs of the inner ear are among the most complex and exquisitely-patterned structures contained within the vertebrate body. Research on the biological mechanisms of hearing and balance requires the ability to obtain high-resolution images of the cochlea and vestibular organs, as well as their associated tissues. Modern optical and electron microscopy can provide excellent imaging data from processed samples and live tissues, but the cost of such instrumentation is typically beyond the reach of individual labs. The most cost-effective method for providing advanced microscopy services to a number of labs is for those labs to form a consortium and share imaging facilities. The present proposal is for the continuation of a P30 project that is directed toward this goal. Specifically, the Molecular and Digital Imaging (MDI) core will provide access to modern optical and electron microscopy to a group of associated labs whose research is consistent with the mission aims of the NIDCD. This section of the proposal has two Specific Aims: First, we propose to provide facilities for optical microscopy (confocal and conventional epifluorescence) to our core group of researchers, along with complete training in the operation of those instruments. The second Specific Aim is to provide access to both scanning and transmission electron microscopy services to this same group of researchers, along with equipment for sample preparation and training in all facets of EM technique. Both optical and EM imaging are heavily reliant on digital image processing, so we will also provide complete computational resources to users of our shared facility. Our core research group is large and diverse, but we are united by many common goals. In addition, we foster numerous collaborative projects, many of which have been initiated and facilitated by the MDI core resources. The MDI core has established an excellent track record of utilization and research productivity. During the previous funding cycle, we have provided imaging instrumentation and training to a total of 37 labs, and data obtained from MDI core facilities has appeared in 56 peer-reviewed publications. In light of this high level of productivity, along with our newly upgraded confocal facility and strong research group, we seek to continue to promote the research of our member labs, and increase existing knowledge of the biological basis of hearing and balance and associated pathologies.